DWG files can contain multiple geometry types, while SHP files contain only one. Each ESRI SHP file stores a single type of spatial data: point, line, text, or polygon. The text SHP files contain attribute text associated with points.
When you export, AutoCAD Map 3D automatically filters the selected objects and exports the correct type of object to the corresponding SHP file. The filenames produced by the export operation use the name of the feature class followed by the geometry type, for example, PARCELS_POLYGON.SHP.
Unless you have modified the MapExport.ini file, choosing ESRI Shapefile from the drop-down list in the Export dialog box exports a single geometry type to a single SHP file. You specify the geometry type on the Selection tab of the Export dialog box.
You can to include all object types when exporting drawing objects to ESRI SHP format. This will remove the object type options and display File Name Prefix field on the Options tab of the Export dialog box, which lets you create a folder of SHP files using this prefix, appended by each object type name.
All objects of the same geometry type will be grouped in a single SHP. For example, if pipes, roads, and streams are all represented by lines, you will export one SHP containing the geometry and attributes for all three object types. If streams have attributes that are not shared by pipes, those attributes will have null values for pipes.
To create polygons in the SHP files using the folder option, you must select the Treat Closed Polylines As Polygons option. To export closed polylines as lines, select the Line object type. To export closed polylines as polygons, select the Polygon object type and select Treat Closed Polylines As Polygons on the Options tab.
This is a separate option on the drop-down list in the Export dialog box that exports multiple drawing objects to a set of SHP files in a folder you specify. Each resulting SHP contains the geometry and attributes for a single geometry type, and is stored in files that indicate that type, for example, PARCELS_POLYGON.SHP.
If you export to an existing file, or to a folder containing files with the same names as those that will be generated by the export, you can choose to overwrite the existing data or append the new data to it. Overwriting can destroy existing files when it creates new ones. Appending adds the data in the current export operation to the existing data without deleting any existing data.
If you are using either the folder or the multi-file Shape option and you choose to append, AutoCAD Map 3D checks the target folder for existing files that use the same feature class name, even if those files do not have the appropriate geometry indicator in their file names. For example, exporting parcels would usually result in a file called PARCELS_POLYGON.SHP. However, if the folder contains PARCELS.SHP, AutoCAD Map 3D checks its geometry type and appends to it if it contains polygon information.